Method and system for gasifying underground deposits of coal



April 1970 HANS-JOACHIM VON HIPPEL 3,506,309

METHOD AND SYSTEM FOR GASIFYING UNDERGROUND DEPOSITS OF GOAL 2 Sheets-Sheet 1 Filed May 16, 1968 L, Li-AQM If I ATTORNEY A ril 14, 1970 HANS-JOACHIM VON HIPPEL 3,

METHOD AND SYSTEM FOR GASIFYING UNDERGROUND DEPOSITS OF COAL Filed May 16. 1968 2 Sheets-Sheet 2 3 wmPw mm Patented Apr. 14, 1970 3,506,309 METHOD AND SYSTEM FOR GASIFYING UNDERGROUND DEPOSITS F COAL Hans-Joachim von Hippel, Muhlenkamp 12, Lunen, Germany Filed May 16, 1968, Ser. No. 729,799 Int. Cl. E21c 43/00 U.S. Cl. 2992 7 Claims ABSTRACT OF THE DISCLOSURE Carbon monoxide gas is produced by conveying hot carbon dioxide gas in a channel which extends through an underground deposit of coal. The hot carbon dioxide gas can be formed by burning a portion of carbon monoxide gas which is Withdrawn from the channel in the underground deposit by way of one or more outlet channels. The burner which produces carbon dioxide gas can be installed in or upstream of an inlet channel which discharges hot carbon dioxide gas into the channel in the underground deposit.

BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for gasifying coal. More particularly, the invention relates to a novel and improved method and apparatus for reacting carbon in underground coal deposits with hot carbon dioxide gas to produce carbon monoxide gas.

In accordance with the presently known procedure, underground deposits of coal are gasified by blowing air through shafts or holes extending into a deposit of coal and by igniting the coal in the bottom zone of the shaft. The resulting carbon monoxide gas is withdrawn by the way of a second shaft which extends through the underground deposit of coal and onto the surface. A drawback of this conventional procedure is that the primary combustion zone travels continuously and in an uncontrollable way, starting from the original point of combustion and on in a direction toward the outlet of the second shaft. Consequently, the quality of gases which issue from the second shaft deteriorates as the point of primary combustion advances below the ground.

Another serious drawback of this procedure is that the rate of combustion, the quantity of carbon monoxide gas, and the rate at which the carbon dioxide gas reacts with carbon to form carbon monoxide. gas cannot be controlled with a requisite degree of accuracy. Still further, free oxygen in the underground excavation reacts with deposits of sulfur to form sulfur dioxide which affects the quality of the ultimate product. Finally, the danger of explosion on mixing of air with methane gas is always present.

SUMMARY OF THE INVENTION It is an object of my invention to provide a method according to which the reaction between carbon in underground coal deposits and carbon dioxide gas can be controlled with a much higher degree of accuracy than heretofore.

Another object of the invention is to provide a method of producing carbon monoxide gas in such a way that the gasification of coal in underground deposits can be regulated as to rate, quality of ultimate product, direction in which the gasification progresses, and location of the point or points where the. ultimate product is withdrawn for further use or storage.

A further object of the invention is to provide a method which can be carried out in such a way that no free oxygen may enter the deposits of coal to thus avoid the likelihood of explosions and/or reaction of oxygen with substances which might affect the quality of the ultimate product.

An additional object of the invention is to provide. a simple apparatus which can be utilized in the practice of my method and to construct and assemble the apparatus in such a way that it can be used with equal advantage for large-scale or small-scale production of useful gases which develop on gasification of underground deposits of coal.

The method of my invention comprises the steps of drilling a network of underground channels including at least one gas-admitting inlet channel, at least one gasevacuating outlet channel, and at least one connecting channel which extends through an underground deposit of coal and connects the inlet channel with the outlet channel, introducing into the connecting channel hot carbon dioxide gas by way of the inlet channel whereby the carbon dioxide gas reacts with carbon in the underground deposit and forms therewith carbon monoxide gas, and withdrawing the carbon monoxide gas by way of the outlet channel. The introducing step preferably comprises burning a fuel in the region of the inlet channel to thus produce hot carbon dioxide gas, and such burning is preferably carried out in a predetermined portion of the inlet channel, i.e., the primary combustion need not be propagated in the deposit of coal as in accordance with the presently employed technique. A portion of the carbon monoxide gas which is withdrawn by way of the outlet channel (for example, about 50 percent of such gas) can be supplied to a burner in or at the inlet channel to react with pure oxygen or air and to form hot carbon dioxide gas which is fed into the connecting channel.

In accordance with a presently preferred embodiment, the network includes a substantially centrally located inlet channel, a plurality of outlet channels which may but need not be equidistant from each other and which may but need not be equidistant from the centrally located inlet channel, and a plurality of connecting channels, at least one between the centrally located inlet channel and each outlet channel.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view of a simple network of underground channels and of an apparatus whose burner is located in the bottom portion of an upright inlet channel;

FIG 2 is a fragmentary vertical sectional view of a modified apparatus whose burner is installed in a horizontal lower end portion of the inlet channel;

FIG. 3 is a diagrammatic top plan view of a more complicated network with several inlet, outlet and connecting channels; and

FIG 4 is a diagrammatic partly vertical sectional view of a further apparatus whose burner receives a portion of carbon monoxide gas which is withdrawn from the network by way of the outlet channel.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a simple network of underground passages, which includes an inlet channel in the form of a vertical shaft 1, an outlet channel in the form of a vertical shaft 2, and a connecting channel 4 which extends through an underground deposit 7 of coal and connects the lower ends of the shafts 1 and 2. The lowermost zone 24 of the inlet shaft 1 accommodates a burner assembly including a burner 10 proper and an upright combustion chamber 3. The lower part of the combustion chamber 3 has an annulus of discharge openings 8 which communicate with an annular space 9, surrounding the combustion chamber 3 and communicating with the intake end of the connecting channel 4. The space 9 is formed in the deposit 7. The material of the combustion chamber 3 is fireproof and the remainder of the inlet shaft 1 is coated with a piping 1a of fireproof material.

Conduits 11 and 12 respectively supply pure oxygen or air and a suitable fuel to the burner 10. The lower zone 5 of the outlet shaft 2 contains an upright chamber 6 of fireproof material which has intake openings 8' and is surrounded by an annular space 9 communicating with the discharge end of the connecting channel 4. A suction pipe 13 is connected to the upper end of a tubular liner 2a of fireproof material which is inserted into the shaft 2, and this suction pipe produces a draft to convey the gases from the interior of the chamber 3, through the openings 8 and space 9, through the channel 4, through the space 9' and openings 8', up the chamber 6 and liner 2a, and into the suction pipe 13. Tar and other ingredients of gases entering through the openings 8' settle in the trough 27 at the bottom of the chamber 6 and can be periodically evacuated from the network, preferably by suction.

The distance a between the shafts 1 and 2 may be rather short or very long, for example, in the range of one, two or more kilometers or miles. Also, the shafts 1 and 2 may be connected by two or more channels 4, which need not be horizontal or exactly horizontal. In other words. the deposit 7 can be provided with a simple or complicated system of channels which extend into all zones of such deposit and which may be horizontal, partly vertical and/or inclined. The openings 8 and 8 need not be located at the same level and the right-hand end portion of the channel 4 may constitute an outlet channel or shaft. The same applies for the shaft 1, i.e., this shaft may constitute a portion of the channel 4.

FIG 2 illustrates a portion of a modified apparatus wherein the combustion chamber 3 of FIG. 1 is replaced by a substantially L-shaped combustion chamber 3', the horizontal portion 24 of which has an open end replacing the discharge openings 8 to discharge hot carbon dioxide gas into one or more connecting channels 4' drilled into an underground deposit 7 of coal. The burner 10' is installed at the junction of the horizontal and vertical portions of the chamber 3' at the lowermost end of the inlet channel or shaft 1, and receives oxygen or air and fuel by way of supply conduits 11 and 12'. The channel 4' may constitute a chamber which is formed during conventional longwall mining and from which the coal was withdrawn by conventional equipment; for example, by resorting to movable roof-support props. In other words, a partially exploited underground mine can be used as a network for installation of my apparatus. Carbon dioxide gas which develops on combustion of fuel in the burner -10 or 10 gradually fills the entire channel 4 or 4, and is hot enough to react with surrounding carbon to produce therewith carbon monoxide gas. Otherwise stated, the channel 4 or 4' constitutes a reduction zone wherein carbon reacts with hot carbon dioxide gas.

FIG. 3 illustrates schematically a more complicated network of channels which include two vertical inlet channels or shafts 1, 16, several vertical outlet channels or shafts 23, 26, which are connected with the inlet shaft 1 by straight and/ or meandering connecting channels 14, 15, extending through one or more underground deposits of coal, a plurality of connecting channels 14, 19, which branch from the inlet shaft 16, and several outlet channels or shafts (not shown) which receive carbon monoxide gas from the connecting channels 14', 19. The outlet shafts 23, 26 may, but need not be, equidistant from each other, and they may, but need not be, equidistant from the inlet shaft 1. The same applies for the inlet shaft 16 and the associated outlet shafts. The outlet shaft 26 is connected with the inlet shaft 16 by a connecting channel 19' which contains a barrier or dam 28, accomodating an explosive charge. The arrangement may be such that the charge in the darn 28 remains intact, while the shaft 1 supplies carbon dioxide gas for the production of carbon monoxide gas in the connecting channels 14 and 15.

However, the charge is ignited and destroys the dam 28 when hot carbon dioxide gas is supplied by the inlet shaft 16, so that the outlet shaft 26 then receives carbon monoxide gas by way of the connecting channel 19. In this way, the operators can control the direction in which the evacuation of carbon monoxide gas occurs and the direction in which the gasification of underground deposit of coal takes place.

The network of FIG. 3 can be drilled in a fresh underground deposit. The meandering connecting channels 14 and 14' of FIG. 3 insure more intensive interaction between carbon dioxide gas and coal during flow of carbon dioxide gas from the inlet shaft 1 or 16. By closing one or more connecting channels and/or outlet shafts, the persons in charge can control the direction and the extent of gasification. When the gasification of coal in the channels 14 and 15 is completed, the flame passing from the shaft 16 to the dam 28 can be used to destroy the explosive charge therein, so that the shaft 26 is then free to receive carbon monoxide gas which develops on reaction of carbon dioxide gas and carbon in the channel 19', such carbon dioxide gas being furnished by way of the second inlet shaft 16.

It is clear that the shaft 1 can continue to deliver carbon dioxide gas simultaneously with the shaft 16, and that the shaft 1 and/or 16 can supply carbon dioxide gas to connecting channels which are much longer than those shown in FIG. 3, and which are being formed while the reaction in channels 14, 15, 14', 19, 19' is in progress. The number and distribution of channels depends on the dimensions of the deposit and on the desired output of carbon monoxide gas per unit of time.

FIG. 4 illustrates a further apparatus which utilizes a burner assembly of the type shown in FIG. 2. The suction pipe 13 has branches 21, 22 and 25, the latter of which is connected to the suction side of a fan 20. The pressure side of the fan 20 is connected with the intake end of the supply conduit 12, i.e., fuel which is burned in the burner 10' of FIG. 4 is the product of reaction of carbon dioxide gas with carbon in the deposit 7 surrounding the connecting channel 4. If it is desired to produce combustible gases of very high quality, the supply conduit 11' is connected to a source of pure oxygen. Such oxygen reacts with carbon monoxide gas in the chamber 3' to produce hot carbon dioxide gas in accordance with the equation 200 plus O =2CO plus 136 calories.

Thus, carbon dioxide gas issuing from the chamber 3 heats the deposit 7' around the connecting channel 4' and reacts with carbon in accordance with the equation 2CO plus 2C=4CO76 calories. It will be noted that the remaining heat (13676=60 calories) is ample to sustain the reduction process and that carbon monoxide gas which develops in the channel 4' is sufficiently hot to expel from coal all or nearly all volatile substances 17 and 18, such as CH and/or others. Such volatile ingredients are evacuated by way of the suction pipe 13' and contribute to the quality of the ultimate product. The branch conduit 25' receives about 50 percent of the total output on carbon monoxide gas. The channels 1', 2' and the conduits 12', 25' provide an endless closed path in which carbon monoxide gas reacts with oxygen to form carbon dioxide gas which, thereupon, reacts with carbon to produce twice as much carbon monoxide gas. The branch conduit 21 can deliver carbon monoxide gas to a plant which produces electricity and the branch conduit 22 can deliver carbon monoxide gas to a pipe line which supplies city gas to private homes and/or industrial establishments.

The walls which surround the channel 4 crumble during reaction of carbon dioxide gas with carbon, and thus provide an infinite number of fresh paths for penetration of carbon dioxide gas into the surrounding deposit. All such fresh paths are surrounded by coal so that the reaction progresses in all directions radially of the channel 4'. This results in a difference in pressures between the channels 1' and 2; therefore, the apparatus should be provided with means for regulating the pressure in the combustion chamber 3' and/or in the supply conduits 11 and 12'.

The output of the apparatus depends on the diameter of the connecting channel or channels. If the network comprises a single connecting channel-e.g., the channel 4' of FIG. 4, which has a width of about 8 meters and a cross-sectional area of about 50 square metersand if the speed at which the gases flow through the channel 4 is in the range of 60 meters per second, the amount of gases issuing from the channel 4' is about 3,000 cubic meters per second. Since the volume of gases increases on heating one can count only with about one-third of the just mentioned volume at normal temperature, i.e., with about 1,000 cubic meters per second. If about 50 percent of the carbon monoxide gas output is used for reaction with oxygen in the combustion chamber 3' of the apparatus shown in FIG. 4, the net output is about 500 cubic meters per second with a heat energy value of about 2,000 calories per cubic meter. Thus, the daily output of such apparatus is in the range of 40 million cubic meters, which corresponds to a daily output of 13 thousand tons of solid coal.

The production cost is but a small fraction of the cost involved in the mining of solid coal. The main expense involves the purchase and maintenance of piping and burner or burners. The number of man hours is reduced by 95 percent and the cost of coal conveying and transporting equipment is eliminated altogether, along with wages for persons in charge of such equipment in coal mining. Consequently, the cost per unit volume of gas which is withdrawn by way of the branch conduits 21 and 22 shown in FIG. 4 is only a very small fraction of the cost involved in the mining of equivalent amounts of coal. All this is due to the recognition that the zone of admission or formation of hot carbon dioxide gas need not travel in the interior of the underground coal deposit, i.e., that the burner or burners can remain sta-. tionary. All auxiliary equipment, such as remote control thermometers, remote control flow gauges, remote control gas quality meters, television cameras for observation of combustion in the burner and others can be assembled above the ground, so that it can be inspected and manipulated from a single point. Such regulation involves determining the rate of combustion and production of carbon dioxide gas to thus regulate the output and quality of carbon monoxide gas. If the apparatus is operated by workmen in three successive daily shifts of eight hours each, each group need not include more than nine workmen, e.g., three mechanics, three electricians and three supervisors. If the carbon deposit contains a relatively small percentage of volatile ingredients, the ultimate product can be subjected to a carburizing treatment prior to being pumped into pipe lines.

Since the connecting channel or channels need not receive any free oxygen (or receive only minimal quantities of free oxygen), the danger of explosion is practically nonexistent, and the likelihood of generation of sulfur dioxide gas is also reduced to a minimum. Furthermore, and since no free oxygen is present in the connecting channel or channels, methane and/or other volatile ingredients of coal are evacuated with carbon monoxide gas to improve the quality of the ultimate product. Since the reduction temperature in the connecting channel or channels is rather low, the cracking effect in such channel or channels is negligible.

The result is a combustible gas whose quality is much higher than that of gases which are obtained on blowing of air into underground deposits of coal. The quality of gases which are withdrawn by way of the outlet channel or channels is not affected by the fact that the reaction zone between carbon and carbon dioxide gas advances toward the outlet channel or channels. If the mine is dry, the burner or burners may receive other types of fuel; i.e., not necessarily carbon monoxide gas. For example, the conduit 12 of FIG. 1 can deliver an emulsion of coal dust in water; this is of advantage because the ultimate product is enriched with hydrogen.

It is advisable to resort to computers which control the aforementioned auxiliary equipment. The computers regulate the operation of the apparatus on the basis of information which includes the temperature and pressure in the combustion chamber on the one hand, and the desired quantity and quality of carbon monoxide gas on the other hand.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A method of gasifying underground deposits of coal, comprising the steps of drilling a network of underground channels, including at least one gas-admitting inlet channel, at least one gas-evacuating outlet channel and at least one connecting channel which extends through an underground deposit of coal and connects the inlet channel with said outlet channel; introducing a fuel and an oxygen-containing gas into said inlet channel; burning said introduced fuel in a portion of said inlet channel to produce hot carbon dioxide gas; introducing only said hot carbon dioxide gas produced in said inlet channel into said connecting channel so that the hot carbon dioxide gas reacts with carbon in the deposit and forms therewith carbon monoxide gas; and withdrawing the carbon monoxide gas by way of said outlet channel.

2. A method as defined in claim 1, wherein said drilling step comprises forming a network with a substantially centrally located inlet channel, a plurality of outlet channels, and a plurality of connecting channels between said centrally located inlet channel and said plurality of outlet channels.

3. A method as defined in claim 1, wherein saidintroducing step comprises combusting a portion of carbon monoxide gas which is withdrawn from said outlet channel to thus produce said carbon dioxide gas.

4. A method as defined in claim 3, wherein said portion constitutes about 50 percent of said carbon monoxide gas.

5. A system for gasifying coal, comprising, in combination, inlet channel means leading to a region of an underground deposit of coal; outlet channel means leading from another region of said underground deposit of coal spaced from said one region, connecting channel means passing through said underground deposit of coal and connected at one end with said inlet channel and at the other end with said outlet channel; burner means arranged in said inlet channel; means for supplying fuel to said burner means in said inlet channel for producing during operation of said burner means in said inlet channel hot carbon dioxide gas; and means for conveying only said hot carbon dioxide gas produced by said burner means in said inlet channel into and through said connecting channel into said outlet channel whereby such carbon dioxide gas reacts with said underground deposit of coal and forms therewith carbon monoxide gas which issues through said outlet channel.

7 8 6. A system according to claim 5, comprising also References Cited means for supplying an oxygen-containing gas to said UNITED STATES PATENTS burner means in said inlet channel.

7. A system according to claim 5, wherein said means 9471608 1/1910 Betts for supplying fuel to said burner means in said inlet 5 2,584,606 2/1952 Memam et 166,59 X channel includes means for supplying a portion of said 3,072,189 1/1963 Macspolfan 166-59 X carbon monoxide gas issuing through said outlet channel to said burner means so that the thus supplied portion of carbon monoxide gas constitutes at least a part of said fuel for the production of hot carbon dioxide 10 166 272 gas.

ERNEST R. PURSER, Primary Examiner US. Cl. X.R. 

